1. Field of the Invention
The present invention relates to a desiccant-containing package for use in an integrated condenser dryer, and more particularly relates to an improved desiccant-containing package for insertion into an integrated condenser dryer chamber of a vehicle or mobile air conditioning system.
2. Description of the Prior Art
Mobile air conditioning systems typically include an integrated condenser dryer chamber or receiver chamber that serves as an accumulator reservoir for refrigerant. The dryer chamber provides a convenient location for a container or package of desiccant material, usually a bag or pouch of mesh material, which absorbs water vapor from the liquid refrigerant reservoir. The desiccant bag performs better when the bag is suspended within the chamber, rather than resting free on the bottom of the chamber. In order to suspend the desiccant bag in the dryer chamber, some kind of fixturing or added parts must be incorporated within the dryer chamber itself or else the desiccant bag may fall to the bottom of the canister tube, making the bag difficult to remove. In systems where the desiccant bag rests on the bottom of the canister tube, a separate filter is normally required because it would not be possible to force all the refrigerant fluid through the entire surface of the desiccant bag.
Desiccant-containing packages are typically employed in relatively small diameter receivers that are juxtaposed along one of the condenser headers in an integrated condenser/receiver for an automotive air-conditioning system or the like. These integrated condenser/receiver structures eliminate the need for separate tubing to connect the condenser with the receiver and have become popular due to their reduced spatial requirements as compared with earlier designs. For instance, the overall dimensions of one integrated condenser/receiver proposed in U.S. Pat. No. 5,813,249 are from about 300 mm-400 mm in height and about 300 mm-600 mm in width.
In the integrated condenser/receiver design proposed in the '249 patent, the axes of the receiver canister and the associated header lie parallel to that of the canister attached to, and contiguous with, the header. The desiccant-containing package positioned in the receiver dries refrigerant fluid (and the oil and moisture entrained therein) before the dried refrigerant enters a supercooler unit formed integrally with the condenser. Ultimately, when the desiccant material becomes saturated with contaminants, the desiccant material is spent and must be replaced.
Due to the compactness of the receiver chamber, it can be difficult to insert, position and remove desiccant bags or cartridges from the receivers of known integrated condenser/receivers. In particular, many known receiver designs require the removal and disposal of significant extraneous materials associated with the spent desiccant bags, thereby increasing the expense incurred during the replacement of the spent desiccant bags.
For example, desiccant package designs are known to include an insert design made through plastic injection molding, including various features to accomplish removal, filtering, and proper positioning of the desiccant within the canister tube. These designs can be quite expensive, both to produce and tool, and do not allow flexibility for different length canisters and/or different desiccant volumes.
Other known desiccant package designs incorporate a disk-shaped filter apparatus into a cross sectional area of the integrated condenser tub. These designs are limited because the filtration area of the disk-shaped filter is virtually equal to the diameter of the integrated condenser tube. As condenser tubes are made smaller and smaller to accommodate smaller and smaller air conditioning units, total filtration area is further diminished. Such a limited filter surface area results in unsatisfactory filtration performance. As a result, it is desirable to efficiently optimize the effective surface area of condenser tube filters.
U.S. Pat. No. 5,666,791 proposes an insert for a vehicle air conditioner. The insert is composed of two parts. One part contains a filter screen. The other part is an extension part bridging the distance from the filter screen to a detachable cover of the receiver.
According to the '791 patent, the part which contains the filter screen and which requires higher manufacturing expenditures may be standardized for several sizes of condensers so that it can be produced in the same shape in large piece numbers. Depending on the size of the receiver, the part containing the filter screen is supplemented by an extension part which has a relatively simple shape and can therefore be produced at a reasonable price in different lengths by means of a modular-construction tool. In addition, the '791 patent teaches that the construction reduces the amount of disposable waste generated when the desiccant material is spent because it will be sufficient to exchange and dispose of the part with the filter screen.
Nevertheless, the insert as a whole is likely to be relatively complex and expensive to produce. In one embodiment taught in U.S. Pat. No. 5,666,791, the container is provided on the inside with a supporting screen. The container, which is made of plastic, is molded around this supporting screen. The supporting screen may consist of plastic or of a special steel, the former having the advantage of being recyclable. In addition, it appears that a filter screen comprising a filter nonwoven material or a needle felt is assembled into the container. This mode of manufacture involves multiple component parts and several manufacturing steps, the combination of which likely increases the cost of manufacture.
U.S. Pat. No. 6,170,287 proposes that a tube of desiccant material be installed and located within a receiver canister by a stand-off component comprised of a tight-fitting, notched, disk-shaped base and a narrow central post which is comparable in length to the height of the inlet above the lower end cap. The tight fit allows the tube to be inserted up into the canister, well away from the bottom of the canister and free of heat damage as an end cap of the canister is attached.
U.S. Pat. No. 6,360,560 proposes a condenser with an integral receiver dryer. The receiver dryer includes a dryer capsule for removing moisture from the refrigerant fluid. One drawback to the dryer capsule proposed in the reference is its relative complexity and likely expense of manufacture.
The dryer capsule proposed in U.S. Pat. No. 6,360,560 is generally cylindrical in shape and includes a base, a housing extending axially from the base and a cap closing an end of the housing. The base is disposed adjacent a seat wall to create a seal and prevent fluid from passing therebetween. The housing has a plurality of apertures extending therethrough and a filter covering the apertures. The dryer capsule includes a quantity of dryer material such as desiccant disposed within the housing. The cap has a loop with an aperture extending therethrough to allow a tool to engage the loop to remove the dryer capsule from the receiver dryer. The loop also acts as a spring to hold the base of the dryer capsule against the seat wall when an end closure is in place over an open end of the receiver dryer.
The end closure proposed in U.S. Pat. No. 6,360,560 has a head extending radially and a threaded shaft extending axially. The end closure also includes a seal disposed about the threaded shaft and adjacent the head. The threaded shaft engages the threaded open end such that the seal engages the side and the head overlaps the side bounding the open end.
It is known to place a fluorescent tracer dye wafer or the like in the desiccant package so that leaks in the refrigeration system can be readily detected by use of an ultraviolet light source. See for instance U.S. Pat. Nos. 5,149,453 and 5,440,910.
Accordingly, it would be desirable to have a desiccant package system that meets packaging and performance requirements in a more cost effective way. Therefore, there remains a need in the art for improvements to desiccant packages which simplify the manufacture, installation and removal of the packages and which minimizes the extraneous material which must be disposed of upon discarding the spent desiccant bags.